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A GEOPHYSICAL STUDY OF A POCKMARK IN THE NYEGGA REGION, NORWEGIAN SEAJose, Tesmi, Minshull, T.A., Westbrook, Graham K., Nouzé, Hervé, Ker, Stephan, Gailler, Audrey, Exley, Russell, Berndt, Christian 07 1900 (has links)
Over the last decade pockmarks have proven to be important seabed features that provide
information about fluid flow on continental margins. Their formation and dynamics are still
poorly constrained due to the lack of proper three dimensional imaging of their internal structure.
Numerous fluid escape features provide evidence for an active fluid-flow system on the
Norwegian margin, specifically in the Nyegga region. In June-July 2006 a high-resolution
seismic experiment using Ocean Bottom Seismometers (OBS) was carried out to investigate the
detailed 3D structure of a pockmark named G11 in the region. An array of 14 OBS was deployed
across the pockmark with 1 m location accuracy. Shots fired from surface towed mini GI guns
were also recorded on a near surface hydrophone streamer. Several reflectors of high amplitude
and reverse polarity are observed on the profiles indicating the presence of gas. Gas hydrates
were recovered with gravity cores from less than a meter below the seafloor during the cruise.
Indications of gas at shallow depths in the hydrate stability field show that methane is able to
escape through the water-saturated sediments in the chimney without being entirely converted
into gas hydrate. An initial 2D raytraced forward model of some of the P wave data along a line
running NE-SW across the G11 pockmark shows, a gradual increase in velocity between the
seafloor and a gas charged zone lying at ~300 m depth below the seabed. The traveltime fit is
improved if the pockmark is underlain by velocities higher than in the surrounding layer
corresponding to a pipe which ascends from the gas zone, to where it terminates in the pockmark
as seen in the reflection profiles. This could be due to the presence of hydrates or carbonates
within the sediments.
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DEEP SEA BENTHIC FORAMINIFERA AS A PROXY OF METHANE HYDRATES FROM IODP SITE 890B CASCADIA MARGINKumar, Amit, Gupta, Anil Kumar 07 1900 (has links)
Release of methane from large marine reservoirs has been linked to climate change, as a causal
mechanism and a consequence of temperature changes, during the Holocene to Late Quaternary.
These inferred linkages are based primary on variation in benthic foraminifer’s singnatures. This
study examines and illustrates deep sea benthic foraminifera from Holocene to Late Quaternary
sample from North Pacific Ocean IODP site 890B,Cascadia Margin. Deep sea benthic foraminifera
has been quantatively analyzed in samples>125 μm size fractions. Factor and Cluster analysis of the
29 highest ranked species made it possible to identify six biofacies, characterizing distinct deep sea
environmental setting. The environmental interpretation of each biofacies is based on the ecology of
recent deep sea benthic foraminifera. The benthic faunal record indicates fluctuating deep se
condition in environmental parameter including oxygenation, surface productivity and organic food
supply. The benthic assemblage show a major shift at 2 to3 kyrs BP and 6 to10.5 BP marked by
major turnover in the relative abundance of species coinciding with in increasing amplitude of interstadial
cycles. There are strong possibilities of methane flux in this site. Dissociation of gas hydrates
and release of methane to the atmosphere could be a cause of increase in the population abundance of
highly reducing environmental species, which we interpreted in our data.
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STRUCTURE OF A CARBONATE/HYDRATE MOUND IN THE NORTHERN GULF OF MEXICOMcGee, T., Woolsey, J.R., Lapham, L., Kleinberg, R., Macelloni, L., Battista, B., Knapp, C., Caruso, S., Goebel, V., Chapman, R., Gerstoft, P. 07 1900 (has links)
A one-kilometer-diameter carbonate/hydrate mound in Mississippi Canyon Block 118 has been chosen to be the site of a multi-sensor, multi-discipline sea-floor observatory. Several surveys have been carried out in preparation for installing the observatory. The resulting data set permits discussing the mound’s structure in some detail. Samples from the water column and intact hydrate outcrops show gas associated with the mound to be thermogenic. Lithologic and bio-geochemical studies have been done on sediment samples from gravity and box cores. Pore-fluid analyses carried out on these cores reveal that microbial sulfate reduction, anaerobic methane oxidation, and methanogenesis are important processes in the upper sediment. These microbial processes control the diffusive flux of methane into the overlying water column. The activity of microbes is also focused within patches near active vents. This is primarily dependent upon an active flux of hydrocarbon-rich fluids. The geochemical evidence suggests that the fluid flux waxes and wanes over time and that the microbial activity is sensitive to such change. Swath bathymetry by AUV combined with sea-floor video provides sub-meter resolution of features on the surface of the mound. Seismic reflection profiling with source-signature processing resolves layer thicknesses within the upper 200-300m of sediment to about a meter. Exploration-scale 3-D seismic imaging shows that a network of faults connects the mound to a salt diapir a few hundred meters below. Analyses of gases from fluid vents and hydrate outcrops imply that the faults act as migration conduits for hydrocarbons from a deep, hot reservoir. Source-signature-processed seismic traces provide normal-incidence reflection coefficients at 30,000 locations over the mound. Picking reflection horizons at each location allows a 3-D model of the mound’s interior to be constructed. This model provides a basis for understanding the movement of fluids within the mound.
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GUAP3 SCALE DISSOLVER AND SCALE SQUEEZE APPLICATION USING KINETIC HYDRATE INHIBITOR (KHI)Clark, Len. W., Anderson, Joanne, Barr, Neil, Kremer, Egbert 07 1900 (has links)
The use of Kinetic Hydrate Inhibitors (KHI) is one of the optimum methods employed to control gas hydrate formation issues and provide flow assurance in oil and gas production systems. The application of this technology has several advantages to operators, including significant cost savings and extended life of oil and gas systems. This paper will highlight a specific case where a Major operator in the North Sea (UK sector) significantly reduced the cost of well intervention operations by applying a KHI in a subsea gas lift line. Considerable cost savings were realized by reducing volume of chemical required and this enabled the application to be performed from the FPSO eliminating the need for a dedicated Diving Support Vessel (DSV). Furthermore, the application of KHI also reduced manual handling and chemical logistics usually associated with this particular treatment. In order to prevent mineral scale deposition occurring in downhole tubing and near well bore and in the formation; scale inhibitor squeeze applications are standard practice. For subsea wells the fluids can be pumped down in to the well via gas lift lines. However, upon completion of previous scale squeeze operations at this particular location, hydrate formation was observed when a mixture of MEG and water was used following interventions via the gas lift line. By applying 1% KHI with a mixture of MEG and Water, the well was brought back into production following scale squeeze operations without hydrate formation occurring.
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EXPERIMENTAL DETERMINATION OF METHANE HYDRATE FORMATION IN THE PRESENCE OF AMMONIADong, Tai Bin, Wang, Lei Yan, Liu, Ai Xian, Guo, Xu Qiang, Chen, Guang Jin, Ma, Qing Lan, Li, GuoWen 07 1900 (has links)
Formation condition data for methane hydrate in ammonia + water and ammonia + water + tetrahydrofunan (THF) systems are very important for the process development and the determination of operation condition for recycling the vent gas of ammonia synthesis using hydrates. This paper focused on the formation conditions of methane hydrate in the presence of NH3 + H2O and NH3 + H2O + THF system. Equilibrium data of methane hydrate in the temperature, pressure and concentration ranges from 277 to 291 K, 0 to 8 MPa, 1 to 5 % ammonia, were obtained. The experimental results indicate that ammonia has an inhibitive effect on hydrate formation. The higher the concentration of ammonia is, the higher the formation pressure for methane hydrate will be.
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EFFECTS OF ADDITIVES ON CARBON DIOXIDE HYDRATE FORMATIONLiu, Ni, Gong, Guoqing, Liu, Daoping, Xie, Yingming 07 1900 (has links)
In this paper, the effect of additives on COB2B hydrate formation is investigated in a high-pressure
test cell surrounded by a thermostated coolant bath. An agitator is configured inside the cell. The
characteristics of COB2B gas hydrate formation with additives SDS, THF and mixture of both were
discussed. It was found that, in a quiescent system with single SDS,hydrate could form rapidly
and the induction time of hydrates formation was reduced, while THF shows no improvement
effect on COB2B hydrate formation. However, the mixture of SDS and THF can promote the hydrate
formation rate considerably, and large amount of hydrates formed. In a stirring system with
mixture additives, hydrates can form completely about 100 minutes early than that in the
quiescent system.
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THE DEVELOPMENT PATH FOR HYDRATE NATURAL GASJohnson, Arthur H. 07 1900 (has links)
The question of when gas hydrate will become a commercially viable resource most concerns those nations with the most severe energy deficiencies. With the vast potential attributed to gas hydrate as a new gas play, the interest is understandable. Yet the resource potential of gas hydrate has persistently remained just over the horizon. Technical and economic hurdles have pushed back the timeline for development, yet considerable progress has been made in the past five years. An important lesson learned is that an analysis of the factors that control the formation of high grade hydrate deposits must be carried out so that both exploration and recovery scenarios can be modeled and engineered.
Commercial hydrate development requires high concentrations of hydrate in porous, permeable reservoirs. It is only from such deposits that gas may be recovered in commercial quantities. While it is unrealistic to consider the global potential of gas hydrate to be in the hundreds of thousands of tcfs, there is a strong potential in the hundreds of tcfs or thousands of tcfs.
Press releases from several National gas hydrate research programs have reported gas hydrate “discoveries”. These are, in fact, hydrate shows that provide proof of the presence of hydrate where it may previously only have been predicted. Except in a few isolated areas, valid resource assessments remain to be accomplished through the identification of suitable hosts for hydrate concentrations such as sandstone reservoirs. A focused exploration effort based on geological and depositional characteristics is needed that addresses hydrate as part of a larger petroleum system. Simply drilling in areas that have identifiable bottom simulating reflectors (BSRs) is unlikely to be a viable exploration tool. It is very likely that with drilling on properly identified targets, commercial development could become a reality in less than a decade.
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COMPLEX COEXISTENCE BEHAVIOR OF STRUCTURE I AND H HYDRATESSeo, Yutaek, Kang, Seong-Pil, Seo, Yongwon, Lee, Jongwon, Lee, Huen 07 1900 (has links)
13C NMR spectroscopic analysis was carried out to clarify the formed hydrate structure in specific conditions on hydrate phase diagram of ternary methane, neohexane, and water system. The obtained NMR spectra at three different conditions suggested that both structure I and H were formed simultaneously and coexisted at 273.6 K and 50 bar. But, for both conditions of 273.6 K, 25 bar and 283.1 K, 50 bar the formed hydrate was identified as structure H only. These results showed that the pure CH4 hydrate of structure I was formed and coexisted with mixed CH4+neohexane hydrate of structure H in low temperature and high pressure region after passing through the phase boundary of pure CH4 hydrate. We have examined the structure coexistence at 273.6 K and 50 bar with other structure H formers of isopentane, methylcyclopentane, and methylcyclohexane. In case of isopentane, the obtained NMR spectrum showed that structure I and H coexisted and the amount of methane molecules in structure I was two times as many as in cages of structure H. However, there were no resonance lines of structure I when methylcyclohexane formed structure H with methane molecules.
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SEISMIC DETECTION AND QUANTIFICATION OF GAS HYDRATES IN ALAMINOS CANYON, GULF OF MEXICODai, Jianchun, Banik, Niranjan, Shelander, Dianna, Bunge, George, Dutta, Nader 07 1900 (has links)
In this paper, we present the results of our recent study of quantitative estimation of gas hydrates in
Alaminos Canyon block 818, Gulf of Mexico. The study was conducted as a part of the JIP Gulf of Mexico
gas hydrates project. Sizable high concentration gas hydrates zones were detected as a result of the study,
with hydrates saturation as high as 80% of the pore space.
Comparison of the seismic prediction with estimation from one available shallow well shows high level of
consistency, adding further to the reliability of the seismic prediction. Based on our findings, multiple wells
are planned for drilling through the high concentration anomaly zones by JIP in the summer of 2008. The
confirmation of our prediction through drilling will lead to the discovery of the first major gas hydrate
accumulation in the Gulf of Mexico.
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COMPUTATIONAL CHARACTERIZATION OF 13C NMR LINESHAPES OF CARBON DIOXIDE IN STRUCTURE I CLATHRATE HYDRATESWoo, Tom K., Dornan, Peter, Alavi, Saman 07 1900 (has links)
Nonspherical large cages in structure I (sI) clathrates impose non-uniform motion of nonspherical guest molecules and anisotropic lineshapes in NMR spectra of the guest. In this work, we calculate the lineshape anisotropy of the linear CO2 molecule in large sI clathrate cages based on molecular dynamics simulations of this inclusion compound. The methodology is general and does not depend on the temperature and type of inclusion compound or guest species studied. The nonspherical shape of the sI clathrate hydrate large cages leads to preferential alignment of linear CO2 molecules in directions parallel to the two hexagonal faces of the cages. The angular distribution of the CO2 guests in terms of a polar angle θ and azimuth angle and small amplitude vibrational motions in the large cage are characterized by molecular dynamics simulations at different temperatures in the stability range of the CO2 sI clathrate. These distributions are used to calculate the NMR powder spectrum of CO2 at different temperatures. The experimental 13C NMR lineshapes of CO2 guests in the large cages show a reversal of the skew between the low temperature (77 K) and the high temperature (238 K) limits of the stability of the clathrate. Good agreement between experimental lineshapes and calculated lineshapes is obtained. No assumptions regarding the nature of the guest motions in the cages are required.
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